Search results for "Complex Mixture"
showing 10 items of 826 documents
Transformation of Iodide in Natural and Wastewater Systems by Fixation on Humic Substances
2000
Separation of different fractions of humic substances (HS) by their molecular weight was carried out by size exclusion chromatography (SEC). The fixation of inorganic iodide by HS of these fraction...
Structurally bound lipids in peat humic acids
2001
Humic acids from highly decomposed peat were subjected to oxidation with alkaline cupric oxide (CuO) at 170°C (single oxidation). Oxidation products were isolated as three fractions, oxidized humic acids, fulvic acids and lipophilic compounds. Isolated oxidized humic acids were subsequently re-oxidized (sequential oxidation) under the same conditions, and released lipophilic compounds were isolated. Lipids released during single and sequential oxidations were determined using capillary gas chromatography and mass spectrometry. Identified compounds accounted for 3.3 and 0.12 wt.% of humic acid content, respectively. Lipid profiles of lipophilic fractions released during single and sequential…
Enzymatic and Chemo-Enzymatic Approaches Towards Natural and Non-Natural Alkaloids: Indoles, Isoquinolines, and Others
2010
Abstract The multi-step enzyme catalysed biosyntheses of monoterpenoid indole and isoquinoline alkaloids are described. Special emphasis is placed on those pathways leading to alkaloids of pharmacological and medicinal significance which have been fully elucidated at the enzyme level. The successful identification and cloning of cDNAs of single enzymes and their application provides great opportunities to develop novel strategies for both in vitro and in vivo alkaloid production in whole plants or tissue cultures, as well as in microbial systems such as Escherichia coli and yeast. Enzyme crystallisation, 3D analyses and site-directed mutation allowed rational engineering of enzyme substrate…
Effects of compost input and tillage intensity on soil microbial biomass and activity under Mediterranean conditions
2010
Organic amendment and tillage reduction are two common practices to contrast soil organic matter decline, thus promoting sustainable cropping and carbon sequestration. In a horticultural land use system under Mediterranean climate, we evaluated the 9-year effects of two compost inputs (15 and 30 t ha−1 y−1, low and high input, respectively) and two tillage intensities (intensive and reduced) on soil macronutrients concentration, microbial biomass and activity. Total organic C, total N and POlsen were smaller in plots amended at low input, whilst intensive tillage decreased them at both compost inputs. These decreases in intensively tilled plots was ascribed to the disruption of soil aggrega…
Effective pair potential between charged nanoparticles at high volume fractions
2017
Simulations of charged colloidal dispersions are technically challenging. One possible workaround consists in reducing the system to the colloids only, whose interactions are described through an effective pair potential, wf. Still, the determination of wf is difficult mainly because it depends on the colloidal density, ϕ. Here we propose to calculate wf from simulations of a pair of colloids placed in a cubic box with periodic boundary conditions. The variation in ϕ is mimicked by an appropriate change in the concentration of counterions neutralized by an homogeneous background charge. The method is tested at the level of the primitive model. A good description of the structure of the coll…
Interaction Mechanisms between guaiacols and lignin: the conjugated double bond makes the difference.
2011
Lignin is considered to be responsible for a selective sorption of phenolic compounds on wood. In order to investigate the mechanisms involved, two similar guaiacol compounds--only differing by the nature of the para side chain--were adsorbed on oak wood extracted lignin. Vapor sorption-desorption isotherms indicated that about 3.5 wt % of 4-vinylguaiacol is adsorbed near saturation whereas it is only 0.8% for 4-ethylguaiacol. For both compounds, the isotherms displayed a hysteresis though significantly greater for 4-vinylguaiacol. Analyses of the hydroxyl stretching region of FTIR spectra of the lignin/4-ethylguaiacol and lignin/4-vinylguaiacol complexes indicated that physisorption via hy…
Effect of storage and composting on the properties and degradability of cattle manure
1995
Abstract Stockpiling or thermophilic composting of cattle manure resulted in significant carbon losses of 17% and 26.4% and relative nitrogen gains of 25% and 32.7% for stockpiled and composted manure, respectively. As a consequence, C/N ratios decreased with increasing time of storage or composting. However, neither the pH nor the mineral nitrogen and organic carbon contents of the 0–50 μm fractions were significant indicators of the transformations of these materials. The degradability of the manure was measured by incubation for 2 weeks in a brown calcareous soil, following 1 week of preincubation. The biodegradation index (BI) or the proportion of CO 2 released from the amended soil in …
The effect of soil on human health: an overview
2018
Soil has a considerable effect on human health, whether those effects are positive or negative, direct or indirect. Soil is an important source of nutrients in our food supply and medicines such as antibiotics. However, nutrient imbalances and the presence of human pathogens in the soil biological community can cause negative effects on health. There are also many locations where various elements or chemical compounds are found in soil at toxic levels, because of either natural conditions or anthropogenic activities. The soil of urban environments has received increased attention in the last few years, and they too pose a number of human health questions and challenges. Concepts such as soi…
Characterization of interaction between tricyclic structures containing pharmaceuticals, their models and humic substances.
2011
Their persistence and wide consumption identify pharmaceuticals as “emerging pollutants”. The complexation of pharmaceuticals containing adamantine ring structures and their model substances with humic acids (HA) of different origins was compared using fluorescence spectroscopy as a function of pH, humic acid concentration, ionic strength, and molecular mass of HA. Binding constants between the studied pharmaceuticals and humic acids were calculated. A combination of dynamic and static quenching processes as indicated by nonlinear Stern-Volmer plots and high Kd values were positively correlated with the concentration of carboxyl groups in the studied humic acids. For basic functional group-…
The impact of Pleurotus ostreatus on organic matter transformation processes.
2012
This study showed the effect of Pleurotus ostreatus on the external organic matter (OM) transformation processes. The kinetics of these changes were determined. The experiment was conducted as 42-day pot experiment done in four combinations (with four replications). The four combinations of different substrates were: (1) organic, (2) composted hay, (3) organic soil + composted hay, (4) organic soil + composted hay + lead. The study results showed that P. ostreatus had the ability to transform external OM as well as metal–organic complexes. These transformations were reflected in the constant rate of characterized changes and correlation coefficients. The study also indicated the direction o…